1. Field of the Invention
The present invention relates to an ink, particularly an ink suitable for use in ink-jet recording process, an ink set, an ink-jet recording process, an ink cartridge, a recording unit, an ink-jet recording apparatus, and a method of improving start-up ejection stability in an ink-jet printing ink.
2. Related Background Art
In recent years, ink-jet recorded images have been required to have high image quality comparable to silver salt photographs that is good in coloring and free of any bleeding. As an important technique for realizing still higher image quality in ink-jet color images, is mentioned control of bleeding at portions of boundaries between inks (hereinafter referred to as xe2x80x9cbleedingxe2x80x9d simply) when plural inks of different colors are applied adjoiningly to each other on to a recording medium (plain paper or the like). Methods for controlling bleeding include a method in which an ethylene oxide adduct of acetylene glycol, or the like is added to an ink to enhance penetrability of the ink into a recording medium. Namely, bleeding can be lessened by causing the ink to quickly penetrate into the recording medium after the ink is applied to the recording medium. For example, Japanese Patent Application Laid-Open No. 8-104837 has proposed inks comprising in combination a dye at least one of counter ions of which is an ammonium ion, and a surfactant such as an ethylene oxide adduct of acetylene glycol, by which printing having good water fastness can be conducted on various kinds of plain paper, and which is excellent in ejection stability even after stored for a long period of time.
As described in Japanese Patent Application Laid-Open No. 8-104837, it can be said that the ethylene oxide adduct of acetylene glycol is an extremely excellent surfactant which can reconcile good shelf stability and ejection stability, which are required of ink-jet inks, with good penetrability into recording media, which is required of control of bleeding. However, in the course of an investigation as to various control methods of ink-jet printers with the requirement for realization of higher image quality of ink-jet recorded images, it has been found that the inks comprising the ethylene oxide adduct of acetylene glycol, or the like involve technical problems in order to achieve a further improvement in reliability while retaining good print quality. More specifically, it has been revealed that when in the course of printing with such an ink, droplets of the ink are ejected from a certain nozzle, and the ejection of the ink from the nozzle is then stopped for a certain period of time without conducting any recovery operation, an attempt to eject a first droplet from the nozzle upon the resumption of the ejection may be accompanied by an inconvenience that the droplet is not ejected, or stable ejection is not conducted, but printing is disordered. The ejection of the first droplet after stopping the ejection for a certain period of time will hereinafter be referred to as xe2x80x9cstart-up ejectionxe2x80x9d. When some inconvenience occurs in the ejection of the first droplet, such an ink is referred to as xe2x80x9can ink poor in stability to start-up ejectionxe2x80x9d.
With the foregoing finding in view, it is accordingly an object of the present invention to provide an ink improved in stability to start-up ejection while retaining various excellent properties exhibited by inks comprising an ethylene oxide adduct of acetylene glycol.
Another object of the present invention is to provide an ink set capable of stably forming high-quality color images.
A further object of the present invention is to provide an ink-jet recording process capable of stably forming high-quality images.
A still further object of the present invention is to provide an ink-jet recording process capable of stably forming high-quality color images.
A yet still further object of the present invention is to provide an ink-jet recording apparatus capable of stably providing high-quality images, and a recording unit and an ink cartridge which can be used therein.
A yet still further object of the present invention is to provide a method of improving stability to start-up ejection of an ink-jet ink comprising an ethylene oxide adduct of acetylene glycol and a dye while retaining the excellent properties of the ink-jet ink.
A yet still further object of the present invention is to provide an ink-jet ink improved in stability to start-up ejection while retaining the excellent properties of an ink-jet ink comprising an ethylene oxide adduct of acetylene glycol and a dye.
The above objects can be achieved by the present invention described below.
According to an embodiment of the present invention, there is thus provided an ink comprising a dye, a silicon-containing surfactant, an ethylene oxide adduct of acetylene glycol, which is represented by the following structural formula (I), and a liquid medium, wherein a weight ratio of the silicon-containing surfactant to the ethylene oxide adduct of acetylene glycol is not lower than {fraction (1/5000)}, but lower than {fraction (1/20)}.
The ink may be provided as an ink-jet ink.
According to an embodiment of the present invention, there is also provided an ink-jet recording process, comprising the step of ejecting the ink-jet ink described above by an ink-jet system.
According to an embodiment of the present invention, there is further provided an ink cartridge, comprising an ink container portion containing the ink described above.
According to an embodiment of the present invention, there is still further provided a recording unit, comprising an ink container portion containing the ink-jet ink described above, and a recording head for ejecting the ink by an ink-jet system.
According to an embodiment of the present invention, there is yet still further provided an ink-jet recording apparatus, comprising an ink container portion containing the ink-jet ink described above, and a recording head for ejecting the ink by an ink-jet system.
According to an embodiment of the present invention, there is yet still further provided an ink set, comprising in combination a first dye having a color tone, and a second dye ink having a color tone different from that of the first dye ink, wherein at least one of the first and second dye inks is the ink described above.
According to another embodiment of the present invention, there is yet still further provided an ink set, comprising respective dye inks of yellow, magenta and cyan, wherein the dye inks comprise an ethylene oxide adduct of acetylene glycol, and the dye inks of magenta and cyan further comprise a silicon-containing surfactant.
According to an embodiment of the present invention, there is yet still further provided a method of improving stability to start-up ejection of an ink for ink-jet printing comprising a step of ejecting the ink, wherein the ink comprises an ethylene oxide adduct of acetylene glycol, a dye, and a silicon-containing surfactant.
According to an embodiment of the present invention, there is yet still further provided an ink for ink-jet printing, comprising an ethylene oxide adduct of acetylene glycol, a dye and a silicon-containing surfactant, wherein the ink exhibits excellent stability to start-up ejection even under conditions such that the ink containing no silicon-containing surfactant becomes unstable in start-up ejection.
By adopting such an embodiment, the stability to a start-up ejection can be greatly improved. Even if a start-up ejection, which means an ejection of a first droplet after stopping ejection for a certain period of time in ink-jet recording, is more or less disordered, a printed image is often scarcely affected so far as a stability to a second start-up ejection, which means an ejection following the start-up ejection, and a stability to an ejection following the second start-up ejection, are good. By making the second start-up ejection and the ejection following the second start-up ejection good, a printed image can be prevented from being greatly and adversely affected even when ejection interval is more lengthened and the start-up ejection begins to be disordered. As an another effect of the inks according to the present invention, the stability to the second start-up ejection and the stability to the ejection following the second start-up ejection are excellent, and high-quality ink-jet recorded images can be stably formed even if the start-up ejection is disordered upon ink-jet recording under a severe environment of, for example, a low temperature and a low humidity. As a further effect of the inks according to the present invention, ejection stability is made excellent, and ink-jet recording can be conducted with good results even when such an ink is continuously ejected under an environment of a low temperature.
When a weight ratio of the silicon-containing surfactant to the ethylene oxide adduct of acetylene glycol in each ink is controlled within a range of from not lower than {fraction (1/5000)} to lower than xc2xd, the improvement in stability to start-up ejection, which is a technical problem on the ink, can be achieved without impairing the excellent properties exhibited by an ink containing the ethylene oxide adduct of acetylene glycol.
Incidentally, Japanese Patent Application Laid-Open Nos. 8-290656 and 8-193177 disclose inks comprising an ethylene oxide adduct of acetylene glycol, and a silicon-containing surfactant. However, these prior art documents neither disclose anything about the technical problem of dye inks to which the ethylene oxide adduct of acetylene glycol is added to make the inks a penetrable system, nor give description suggesting the effect that the technical problem can be improved by adding a specific amount of the silicon-containing surfactant.